HomeMy WebLinkAboutGrading Plans - 07/25/2024 KEEFE CIVIL, INC
— 3125 Crockett Street
/ Fort Collins, Colorado 80526
���� (970)215-6808
1 meg@keefecivil.com
May 3,2024 Keefe Civil Project Number: 2024-006
Water Utilities Engineering Building Permit B2403704
City of Fort Collins Blake Lot 47
700 Wood Street
Fort Collins, Colorado 80522 Grading/Stormwater Plan Accepted
RE: 730 Colorado Street Drainage Memo (Building Permit Released)
Accepted by: Dan Mogen
To Whom it May Concern: Date: 07/25/2024 - art o ins
The purpose of this letter is to describe the proposed site improvements and potential drainage
impacts at 730 Colorado Street(Exhibit A). The 0.18-acre project site is an undeveloped single-
family residential lot with native grasses located on the east side of Colorado Street between Laurel
Street and Locust Street in Fort Collins, Colorado (Figure 1). The site is located within the Old
Town drainage basin.
H
C
♦ f
t,.
Project Site
1� l < <
fi
is _ �� 4r117t
1
',p
c.
Figure ]:Vicinity Map
la m is d a a a a11121 a 9112193 a 11 a a Is e e ds >a Isis a
'� Q Q Q % Q Q Q Q Q 9 Q Q Q Q Q 9 Q Q Q Q Q Iq
730 Colorado Street Drainage Memo Keefe Civil Project No.: 2024-006
Page 2 of 3 May 3, 2024
The lot is bound by existing single-family residential properties on the north and south lot lines,
Colorado Street right-of-way to the west, and an abandoned alley to the east. The abandoned alley
has existing utilities in it,but it is a grassed area contained within the project site's fenced area.
Adjacent lots also have the alley way contained within their backyards. East of the site's perimeter
fence is Laurel Elementary.
CTL Thompson(2023) completed field investigations at the site,which included one bore drilled
to 12 ft below ground surface. Groundwater was not observed during investigations and subsurface
conditions were observed to consist of sandy clay over gravelly sand. Per the NRCS Soil Survey of
Larimer County(Exhibit B),the site entirely consists of Fort Collins loam and is classified as
being within hydrologic soil group C. These soils are anticipated to have a slow infiltration rate
when thoroughly wet and a slow rate of water transmission.
Per the flood insurance rate map, the lot is located within Zone X. Zone X is defined as an area of
minimal flood hazard and does not have a base flood elevation associated with it. Also, the site is
outside of any City of Fort Collins mapped floodplains. (Exhibit C)
Historically, site stormwater has drained with gentle slopes from the west to the east, onto the
existing alley way and Laurel Elementary property(historic basin A). Historic and developed
drainage basins are shown in Exhibit D.
The proposed site improvements include a new single-story home with basement, and a concrete
patio in the backyard. The grading plan was developed per Fort Collins Stormwater Criteria
Manual(2018) site grading design for a Type B lot and has resulted in two developed drainage
basins. Developed basin A will encompass most of the front yard and the driveway and will drain
into Colorado Street right-of-way. The remainder of the site will be developed basin B and will
drain into the abandoned alley area,which discharges into the Laurel Elementary property at the
northeast corner of the lot(Figure 2). Once the stormwater makes it onto the school property, it
enters a grassed swale area, and drains out to a school driveway,which outlets into East Laurel
Street right-of-way to the north. See Exhibit E for the field verified offsite drainage patterns.
Z
S
Figure 2: Looking north at drainage outfall onto Laurel Elementary property
d a a Is gold d d d d d d a d ic is a a d d d d a d d 9
a 42 a 12v 12 Q 42 a v 12 v a 1212 a 12 42 4 v 12 v o v 02 14
& e LSAAAAAAAA A d A 1 & e & A A A e � 1 �
730 Colorado Street Drainage Memo Keefe Civil Project No.: 2024-006
Page 3 of 3 May 3, 2024
Where possible, impervious areas and downspouts shall be routed into pervious areas with
landscaping to allow for project stormwater infiltration and increased water quality with site
runoff. Since the lot's total adjusted impervious area increase is below 5,000 square feet(sf),water
quantity detention requirements are not required for this development.
Adjusted Adjusted
Overall Site Hardscape or Hard Historic Site Historic Developed Developed
Surface Areas Areas Site Areas Area s
Concrete 0 0 1,015 1,015
Rooftop(90%) 0 0 3,350 3,015
Total Impervious Area 0 0 1 4,365 1 4,030
Adjusted Site Imperviousness 1 4,030
The composite runoff coefficient and drainage basin runoff calculations for the historic and
developed site are included in the enclosed tables (Exhibit F). Using the Fort Collins Stormwater
Criteria Manual(2018), it is estimated the proposed stormwater runoff from the site will increase
with development. However, it is my professional opinion that the additional runoff generated by
these site improvements will not cause adverse impacts to downstream private properties prior to
reaching public property in either Colorado Street or East Laurel Street.
I hereby attest that this letter for the final drainage design for 730 Colorado Street was prepared
by me or under my direct supervision, in accordance with the provisions of the Fort Collins
Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not
assume liability for drainage facilities designed by others.
Thank you for the opportunity to submit this drainage memo. Please do not hesitate to reach out
to me if you have any questions or comments regarding the above items.
Best regards, �o�),p,DO LICFyd'
VOA�PN L.
F•
05//03/24 m
39378 i
• oipitalry signs]by •
Megan L Keefe •
Reeson.l attest fa iM1.
occur antl lydegri.
of ma aeeemem.
0
Megan L. Keefe, PE/Manager ^as810NAI-ENG\
Keefe Civil, Inc.
Enclosures
Cc: Steve Josephs, Craftsmen Builders
References
CTL Thompson. 2023. Soil and Foundation Investigation for 730 Colorado Street. Project number
WY02232.000-120. August 15, 2023.
Fort Collins Stormwater Criteria Manual. 2018.
a a91 d a is a Is 12 a a a a a a a
� e e e � e e � e � a � e e �► � a � � � � e � � � f
EXHIBIT A
0N60
W O311A100303039S3NlUZ l9O3L6W ��--_
0(1"0100'SNI11001a0J
9Z90000'SNIIIOO IHOJ
� L�TL
1381S1NOOWMC NY-ld E)NIQ�uD O
0NI`llnl0 3J33H IM iS 0dVi10100 0£L izi De
M.
o� e
h4� _} '
•_ 0
\ V mr IfIII g�
po3
all
o8ggoo
M �3
�Nm
LLo � a
"gypgq 7 fig_ �� 89N a p
s a
non
w o z3w¢7 f �
_ o
wm
Opya0700 ^� �� m� z� o� '°� osoyy <
w ss ss ss ss ss ss� sF'� _`zo �o �o Gz ��WmWWo�� �
�i ge �9a oo w �z�z3LL OF�r�
F=a4� 08
EXHIBIT B
z z
F �
� 3
56L16bb L8Ll,w 6LLL6bb W1,63b fi Mtt 99M" Lt7LW" N
M,Lb,£oSOT M„Lb,£oSOT O O
N r
�— N O
N �
Cl) m
d
ti
v '
O
a
(0
O
O
U
C T
d O
Q i
O
O
O O
U N C
ago � >
m `o O
o U n
�o � 0
2co >
o
p v v ar m
m
�� Z
0
0
a i p
w
S
c
x
p o `o
� aj
CL
� •-� � `n o v ✓A
O =
- N �
rya N Q'
zQ ZU
M„OS,£oSOI I - M„OS,£oSOT Q
S&W" L&W" 6LLL6bb 6LL 66Tt £ZAM, 99266bb LbL1,6tt
z z
F
aM
Q V�
P �V1
vv
C) 0
_ O N m N N N
a) N �O �., N N O)
N NN to m 7 N M m
N O — N a) a) tf m N a a) ¢ 3 c o d
m U > O a Q U O U O a m I N � C_
a C U cn O E ? N N C 2 E
c- rn D E � as a�i o m N — Y m
Z c cCL �i �6 m o a� a - 0 m " a E C�i ion a o
to cr m _ N
Q E m av m m N 0 0 not U oM o` ) c
m N E Co N c L � M CO t m Q m O O M 7 m
3 N a) c7 NZ z U UE � �
Q t/1 O) a) O N (n a a) m N
L L cc C d m a N O m Q (6 o N L ° a)
O a) a3N E U w mm � oa) a) s 3 � C) a)
a_ CL
N mL aa)) r `o o �N n Q m v m o a) >
O 0 E Na m i m `o m - m a) m
a) U O C
LL a) w ° c > c o' �� c � c E2 o' Cr N t E �C) N
Z �' a r m oL O Za 2 a) m o � U c m o a) m E °)
Ec >,-0w :2 m a U) (Daa)) ° N a � o mo 'nm
o a) a)vUi m a) - - o', � m E � a) � 2a)
Q U NL'' U 7 J N fl.'C O f�6 —_ m j L a C O
(6 E EL O a) m m ( Q U C a) N J a) O N O
w m E c� N w Z � 3 � m m � nm id m a E o 'v)aai
a) O a C N O. N >. a) U CO m 7 N a d Q N O a CO CL
m
Z o cma) N oa) CU 2m � 3cmca Uo > m c , ns LcyE
U) a) � E o) >.E U) ( E m m U m L m o `m o.m _
N M a) U 'C o— m O O a) a) a m Z Q O.O m a a 0
'p C m a m N a) 7 a) O C ,� U > 7 >, m C) 'C O)
CL
U N M '� C fl. m N N LCl) "a N U C N a a) (n O E M N O .a a) C
@ L N m C N C O U a) a) O a) o m O N U L ,� 0 7 O �? m C) L p m t
O � � W E — U N d E U) 2 a i5 m H 0 cn to cn — O N H U E N
0
U
as �
2 m
a z
1
o aa)
UC-� Zcn
a`) oCf) .>
.1 m = m
m o d o a)
0 o
U f0 Op
N
O M @ CL m
v N
C O O) N N 0 O
.O O C = N N 'co
U) -p N a) d O N O
-Cz
E o � � d
@ mN 0, 6 N0 O (
O '0 U U U z U) Q
a Y �
Q W
Z 0 0 00 aLU
`
« N Y
cu
C
LU
J �
a
0 co
y O 0
U C G
N y O O
^ C
0 C" N N N
Q 0 T W N C
C
w d d U 0 0 a J U U o d O
a a) a `a m m
y c c c y
U
Q fn O C
N G
O N
. c
m o
z U
r1
Hydrologic Soil Group—Larimer County Area,Colorado 730 Colorado Street
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
35 Fort Collins loam,0 to 3 C 0.2 39.5%
percent slopes
36 Fort Collins loam,3 to 5 C 0.2 56.8%
percent slopes
54 Kim loam,3 to 5 percent B 0.0 3.7%
slopes
Totals for Area of Interest 0.4 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D)and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential)when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential)when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
usDA Natural Resources Web Soil Survey 3/22/2024
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group—Larimer County Area,Colorado 730 Colorado Street
Rating Options
Aggregation Method: Dominant Condition
Aggregation is the process by which a set of component attribute values is
reduced to a single value that represents the map unit as a whole.
A map unit is typically composed of one or more "components". A component is
either some type of soil or some nonsoil entity, e.g., rock outcrop. For the
attribute being aggregated, the first step of the aggregation process is to derive
one attribute value for each of a map unit's components. From this set of
component attributes, the next step of the aggregation process derives a single
value that represents the map unit as a whole. Once a single value for each map
unit is derived, a thematic map for soil map units can be rendered. Aggregation
must be done because, on any soil map, map units are delineated but
components are not.
For each of a map unit's components, a corresponding percent composition is
recorded. A percent composition of 60 indicates that the corresponding
component typically makes up approximately 60% of the map unit. Percent
composition is a critical factor in some, but not all, aggregation methods.
The aggregation method "Dominant Condition"first groups like attribute values
for the components in a map unit. For each group, percent composition is set to
the sum of the percent composition of all components participating in that group.
These groups now represent"conditions" rather than components. The attribute
value associated with the group with the highest cumulative percent composition
is returned. If more than one group shares the highest cumulative percent
composition, the corresponding "tie-break" rule determines which value should
be returned. The"tie-break" rule indicates whether the lower or higher group
value should be returned in the case of a percent composition tie. The result
returned by this aggregation method represents the dominant condition
throughout the map unit only when no tie has occurred.
Component Percent Cutoff: None Specified
Components whose percent composition is below the cutoff value will not be
considered. If no cutoff value is specified, all components in the database will be
considered. The data for some contrasting soils of minor extent may not be in the
database, and therefore are not considered.
Tie-break Rule: Higher
The tie-break rule indicates which value should be selected from a set of multiple
candidate values, or which value should be selected in the event of a percent
composition tie.
usDA Natural Resources Web Soil Survey 3/22/2024
Conservation Service National Cooperative Soil Survey Page 4 of 4
EXHIBIT C
m'o yg
s y�r QW oY L ; �� ; oppOc° �✓o1 d�v:.. ¢yO .a Qa S_9�°o l9. Lo c4C ' 'µ _ EL
V OC O V 23 Qyc r`e°y�j. Yo ppp� Ero vN
LL ° ; KO O
m a ° c a E mY �m � 'i-
= m � q C' v o y a ��
�i o L cLi c o x 8 ME C< �v g c E L m �
X ° U i. N •�— 9 2 " p ° C V a 9 ° $ m N+ v a «�•' p V 0 m
`•' �s > > '" a °o rc 99!! 4. 'c o ti
NE � `onlee �a
m � o ; o c Q � 4 �. o � o Y e'3 m m m� �0 3 � m�
3aCo E '� oa �o < s y
m :3 � U a S o Z m �y 4 w E ° 2 E 3 $ �
55 m
U c�
® a m w N c c a L V 9 0
y V _~ 9 m m C n C m m �N E °m > aE m
-ar
O � Oq 0 Qswu • ww gym $ t2 ° �2n '6M ` � C,
w o N o v$
d ad w _a d Z V O� Q a 40 m o'aZ E E c� n6
4c q� QD w C7 0- '^nom of m m m m K E
J W w = O 0
h � �
} 2 l7
7 y - N
CL
a
wl
c�
r LL ��'"
U
�1f1 0 - _I
r� 0m00��� O f�.� •• 11�� 1 .►1 O
air
CL
W e I 0
.}.� 1 O
rl
LL
..
LL ti
lV � • � ' w �� r
•
fi w�.Q
N ' r'• � . � - :�
o
°o
(j5 0 0 o
0
O Y
w y m LL O Of •_ •`�
` N
0 2 = w a rn m o o 0 0
LL w w w O E
CLL LL LL U U U J U
Cd
LLJ
N U
Z Z �
4 V C Vl
Q0 m
m
C
U
w a) m
C a N
- O m
m
U s
t o w
LL E2
L T M C
00 _ N
U m �
-C
E >(Q
O C
O U
U
- 7 U m
O y
U � C
m O m
N - oyE
': w o
Y C
m m N
c m E
m.+
_ m
w g'E
O-
m m
w m
O n N
E E
F
LL
�r Cl)
O t -
L • � o
O �
M
ti
t
a
Q
O
U
m r
ii
EXHIBIT D
0N60 11�103333NU93W OOVHOlOO'SNIllOOlaO3
1 WOO' ��--_
t ,�'�EFE � 0009SlZ lOL6) � T
Z �� ''� 0Z90000'SNI11001tl03 - " LL
e oi. jy 33tl1Si3N00 0921E ,,f 1191HX3 3E)VNIVEIG p
c o•=:...e° ONI'llAlO3d33H
IM3 IS 0dVi10100 0£L
DQ
z
e�
W
vp \R z Z
\ 00
w
w z
wO
¢v
\ LL
o
a, 0 0
o
z
I
o 25 /
�a°
I ul d rc ui
I U 6 j v w
a
° w
_ w
I s s
/u � � II 3 m :♦ Q OQ � �
I o \ a
I � e
o �
'o w ■ i
�0o = 3LL =o
■
<2 R,w� ��m age ■
EXHIBIT E
fir► ' +d�� �;-
a�
t (.
»i• �Y �AN
1.
ry
7.1
in
ai , I O W r
a �
YVI
40,
Aw
" � -�;. .,,r � - }�' M W ^d .d r/ w� � r r�rFrrevrr, •.FriF- --
■
,i � 8 ,y _'Y - • � Yam+,.rpi3� � 1
p
•;9. - � /` Fes,
n.: ._J - «sy� �1 t V }�_ �� 1 7 -.J +r.-. �, •ram I•,� .� .. .
4i:
NEW
IT •
EXHIBIT F
- \ \
\ \ � (
bb
20 0 ID 0 \
10
{ 2
cr
< \ E 00
< < ( 4 ( (
°
bD
d \ \ ( \ \ \
< m > f /
\ Q \ \ j � \ { k \ / j \ \
« J2o
\ { \ \ �_ �
k k § k k; \ ) ) / / § � � � � � 2
u \ —
\ 2 , u } &
l C,
)
0 0 0 (U
} 7 } } ) \ k
\ 0 of \ \ } - {
E E2 k � (
C 3 / 2 L \ } ! —
§ ^ ® cr
/ \ < ; \ _
CD \ /
CD \cc } ) � {
0 < 0 8 g G G
2 ) S ,
: \ ) E £ �
cc 0 } ) ) »
\ / 7 -
E3 / CL
/ \ 0. \ � �
\ , \ m e
— t / f e
) ) \ �o \
o
® ( [
\ } \ } ) \ } \ \ \ / \
oo m -i
C m N N
w O O 0 -1
of
p ? cI O It �_ O
U. O O O 7 +'
c cr N 7
cr
A
L 00 Ln 00 N W
>• O O N �
N O O O O
aj
Y C
L :
> Ln un In c >
o �o rn m E ra
t o rn of Ln —
c
o
> -1 00 00
.n m a E ate+
cu E 3
c o`qq o`q o`no c E
N c N N E 0
Y
Q N
u �n
m c r
c .5 C) 0 = In
m ��I n ui (Yi �j c
0LL N
c H aJ
C �Ln N 00 V) Lu in V
C r-I m N -i5 m
C
9 6 C
m ro c -n
+l
0 0 ° u E v)
L
U aYi U 0 C O
c N > c
76
o v E c ° E aco
o, te(' Y 0)
H
N O O Y O C Y
C +fo V0 v — 0 X
u O F c C. Q Q v� C .d I co O C N C C N
C� m Z Z N — — ar 7 L ao
m 0) o II -0 o o_ z Q
V U u U K
w O m o oa F` ~ II II II
O LL H u ar O O Q U — Q -O
y L C- LL LL
7 d Q O O V
GC u)O (D ar v v v u1
y _ d N a a o II r o
c p
H p cri uiLA 0' a
m O
0
a! i In U
w O c m
O
m O J n
Cl
Y
M Y ^�
o r^ 00 rl w
io
� cu
01 E
E
v
LO �_ N In '
C
�r1
m 5 E 4 m N v
Y
9 ' 3
O y v
ca O 'OR N N -ZT N C m `
m m fa
C m m II
Y O O O
4Y- In 0 0 ++ N E ++ N O
J c
N C 0 Y N O U
V io O Y N iu
7 y) U W 7 C
a+ C c - c ar Y
O p m 0000 r E 3 E >
co E o 0 o a
` Y Y Q!
O N +' Y O U C aJ w
V i C 'A c i C a) ..�„
m 0 'u ai
a) O u
" U al j O
c v 0
L *�' v a O u - O m -
0 L r0 N U r0
cc o N rl � 3 u c o v C3 a N °C c
EE O X 0 O" o O - O a0+
ro
V an V ly" Ln O ll a1 0 an M O c bo
J V7 C Q) 0 O
II >
II II = N 2 J
a) 00 N In O 1- U U J LnO a" II 11 II II
i U cq U a l C 5 V7
Q m O O O
-C " II L v II
a a m a F" a > 3 a` t=
10 o
m Z r4 N